Tyrannosaurus rex grew faster and weighed more than previously thought, suggesting the fearsome predator would have been a ravenous teen-ager, researchers said Wednesday.

Using three-dimensional laser scans and computer modeling, British and U.S. scientists "weighed" five T. rex specimens, including the Chicago Field Museum's "Sue," the largest and most complete T. rex skeleton known.

They concluded that Sue, who roamed the Great Plains of North America 67 million years ago, would have tipped the scales at more than 9 tons, or some 30 percent more than expected.

Intriguingly, the smallest and youngest specimen weighed less than thought, shedding new light on the animals' biology and indicating that T. rex grew more than twice as fast between 10 and 15 years of age as suggested in a study five years ago.

"At their fastest, in their teenage years, they were putting on 11 pounds or 5 kilograms a day," John Hutchinson of the Royal Veterinary College in London told Reuters.

"Just think how much meat that is. That's a hell of a lot of cheeseburgers ... it's a whole lot of duck-billed dinosaurs they needed to be chowing down on."

Hadrosaurs or duck-billed dinosaurs were common plant-eaters that lived alongside T. rex, making them an obvious meal for the giant meat-eaters.

A huge appetite means T. rex would have needed extensive territory and they were probably relatively rare. Their rapid teenage growth spurt also suggests they must have had a high metabolic rate, fuelling the idea they were warm-blooded.

A large body mass would have come at the expense of agility and the lower-leg muscles of T. rex were not as proportionately large as those of modern birds, indicating a top speed of about 10-25 miles per hour. "It's not super-fast but they were no slouches," Hutchinson said.

The latest research, published online in the journal PLoS ONE, adds to the body of evidence that has made T. rex among the most intensively studied of all dinosaurs.

The researchers, led by Hutchinson and Peter Makovicky of the Field Museum, used scans of skeletons to build digital models and then added flesh using the structure of soft tissues in birds and crocodiles as a guide.

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